1. Field of the Invention
The present invention is directed to a device for controlling the movement of a web of material being fed at a constant rate of speed through a web take-up device to a machine which acts on a portion of the web as the portion is at a standstill. The web take-up device includes a pair of first members mounted in a side frame for rotation on a first axis, a cylinder guide member for engaging a portion of the web and means for eccentrically mounting the guide member on the pair of first members so that it rotates about the first axis with the amount of offset or eccentricity being controlled by a control screw.
2. Prior Art
In one known method and apparatus for forming blanks utilizing a platen press, a web of material, for example paper board, is generally delivered to the platen press in a continuous manner. In view of the fact that the platen press is able to die cut a portion of the web if this portion is temporarily stopped or at a standstill, continuous feeding of the web causes the web to accumulate in front of the cutting station of the platen press. To overcome this problem of accumulation of the continuously moving web, several solutions have been suggested and tried out.
The most simple solution consists of forming a loop in the web prior to its introduction into the press. However, fluttering will occur in the loop and this solution has been found to be unsatisfactory when the production speed is increased and when the accuracy of the position of the web portion introduced into the platen press must be maintained in order to obtain a registry between the printing on the web and the die cut pattern.
Machine builders, therefore, imagined a way to check the formation of the web loop in such a way that the effect of fluttering on the web would be reduced to a very minimum at the point of entry to the machine by using a loop controlled device. For this purpose, an appliance was used which involved a web being lead around a circumferential portion of a roller which is mounted between two rotating members or plates with the axis of the roller being offset from the axis of rotation of the plates. German Patent No. 1,061,167 of July 6, 1957 is an example of this type of apparatus.
Another solution, which has been suggested, was disclosed in U.S. Pat. No. 4,060,187. However, the solution of this patent has various disadvantages with regard to the adherence of the broad web-like material on the roller when operating at high speeds, for example, with a linear web speed of up to 300 meters per minute. With a low traveling speed for the web, the web adherence on the revolving roller is good and the rotary motion of the offset roller corresponds to the web traveling motion. On the other hand, in the event of high speeds, the web begins to skid or slip on the revolving roller. Consequently, the curve represented by the angular motion of the revolving roller varies from the curve represented by the web travel and will therefore, in practice, lead to misregistry and increase the temporary stresses which interfere with the web traction. Thus, the use of the rotating roller has the consequence of subjecting the web to a heavy overload to cause misregistry of the pattern due to the stresses on the web. In addition, the rotating roller will generate a lot of noise which occurs from the web sliding on the roller and from the excessive pressure which must be exerted on the web in the area of the nip rollers which are being used to feed the web onto the web guide member between the pair of first members.